There is no rule or policy requiring special counsel Robert Mueller to complete his investigation 60 days before the midterm election, despite what the president’s lawyer Rudy Giuliani says. For starters, Donald Trump isn’t on the ballot. Even if he were, there’s no reason that an investigation of him or his 2016 campaign would have to be completed in advance of an election.

What is true, however, is that there is a strong unwritten norm for the Department of Justice to avoid taking public prosecutorial action around the time of an election — a period thought to be about 60 or 90 days before it. Mueller and his team are well aware of that norm.

It seems probable that Mueller will follow it, at least to the extent that it’s practicable. He certainly should. If he does, that means you shouldn’t expect any major indictments or other revelations during the next 60 days.

Mueller will follow the unwritten norm not because he’s soft on Trump. Rather, Mueller knows better than anyone that Trump’s assault on the U.S. criminal justice system has been in large part an assault on exactly such unwritten norms.

In particular, Trump has systematically sought to undermine the hard-won norm that investigation and prosecution should be nonpartisan and unconnected to electoral politics.

Firing FBI Director James Comey was just the most salient example. Trump has also sought to break the norm by saying that the Department of Justice and the FBI are politically motivated. He’s consistently broken the norm himself by calling for investigation and prosecution of Hillary Clinton and other Democrats.

The unwritten 60 (or 90) day norm is a perfect example of the aspiration to nonpartisanship that Trump is trying to break. There is no perfect way to make sure that investigations don’t affect politics. But one way to approximate that objective is to create a buffer between major announcements and the election.

Comey’s October 2016 announcement that the investigation of Clinton’s email server had been reopened demonstrated very clearly why the unwritten norm is so valuable. Comey broke the norm. Whether that affected the outcome of the 2016 election is not a matter subject to objectively verifiable fact. But Comey’s violation of the rule certainly created the perception that his and the FBI’s actions could have affected the outcome. That fact has loomed over U.S. politics ever since.

It seems pretty unlikely that anything Mueller could announce before November’s midterms would materially affect the electoral outcomes. But that’s just a further reason for Mueller to wait and announce anything significant only afterward.

Mueller and his team have to be completely above suspicion, like Caesar’s wife. They must bend over backward not to play into Trump’s attempts to depict them as partisan. If you prefer a different metaphor, they have to be more Catholic than the pope.

That would be true under any circumstances where a special counsel was investigating the president. But it’s much more important given that the investigation is focused on a president who is trying to break unwritten norms of nonpartisanship.

The fact that the investigation also touches on Comey and his firing adds further reason to avoid even the appearance of potential partisanship, not that another reason is needed.

In short, the whole issue of unwritten nonpartisan norms is swirling around this presidency and the Mueller investigation of it.

No doubt some Democrats will think that Mueller should charge forward with his investigation and let the chips fall where they may — especially if it leads to greater public outrage at Trump.

That would be very shortsighted. The point of the Mueller investigation should not be to undermine Trump presidency. Rather, the point is to begin restoring public faith and confidence in governmental institutions by showing that the government can find and tell the truth in an independent, nonpartisan way.

Democrats shouldn’t fall prey to the temptation of following Trump’s lead and believing Mueller is out to get the president for partisan reasons. He isn’t. Mueller embodies precisely the ideal of a nonpartisan criminal justice investigator and prosecutor.

When it comes to the Mueller investigation, the truth should at least help set us free. We can hear that truth any time, including after the 2018 midterms are over.

Noah Feldman, a law professor at Harvard University, is a columnist for Bloomberg Opinion.